A wireless local area network (WLAN) generally includes one or more Access Ports (APs), and several wireless client devices which communicate with the wired network via the APs. As the number of APs increases, the network becomes more difficult to manage. To help alleviate this problem a master controller sometimes referred to as a “wireless switch” can be added to the network which controls one or more APs. A wireless switch controls some or all of the APs in the network, and data going to or from the APs flows through the wireless switch. This way, a single wireless switch can have multiple, geographically distributed APs connected with overlapping coverage areas.
Because mobility is a key driver in the deployment of wireless networks, most WLANs attempt to give wireless client devices (WCDs) the ability to “roam” or physically move from place to place without being connected by wired connections. In this application “roaming” generally describes the physical movement of a WCD between APs. When a WCD moves or “roams” out of the communication range of its original AP and into communication range of a new AP, the WCD re-associates with the new AP after a certain period of time. A typical roaming time on an encrypted link from the original AP to another encrypted link on the new AP is between 20 and 50 milliseconds or more for networks which include wireless switches.
However, in many cases the delay or latency which occurs between the time when the WCD begins roaming and when it finally re-associates with its new AP is insufficient. In many cases, all of the packets transmitted from or to the WCD will not be received. For example, when the WCD has an active call or session that is being communicated through the original AP, during the time which elapses while the WCD is roaming from its original AP to its new AP, packets sent from the original AP will be “dropped” and will not be received by the WCD. Likewise, packets sent from the WCD to the original AP will not be received by the original AP. As such; there is no way to guarantee that the packet(s) from the original AP will reach the WCD when the WCD is out of the range of the original AP, and vice-versa. Roaming is costly for time-critical applications, such as voice applications, since several voice packets might be lost during the roaming interval especially in networks which employ wireless switches since these networks have high latency layer 3 (L3) tunnels between the wireless switch and the APs controlled by that wireless switch.
One approach to solving this roaming problem is to delay/store packets and then retransmit the same packets through the new AP, after the WCD moved to the new AP. However, in a time-critical applications, such as voice applications including Voice-over-WLAN, delaying a packet for more than a certain amount of time (e.g., 30 ms) is essentially the same as dropping it, and therefore this approach is not viable.
Another approach to solving the roaming problem is to have all APs configured as part of the same Basic Service Set (BSS) and to operate on the same channel. This way the entire coverage area appears to be covered by a single AP. However, with this approach a very low latency link/tunnel is required between the wireless switch and the APs since the beacons from each AP must be tightly coordinated so that wireless communication devices do not get confused regarding the beacon timings and bit mask settings. This rules out implementing a L3 tunnel between the wireless switch and the APs controlled by that wireless switch.
Accordingly, it is desirable to provide improved wireless switching methods for allowing a wireless client device to move between access ports without losing or dropping packets. It would also be desirable to eliminate the roaming problem in a way that is independent of the type of tunnel between the wireless switch and the APs controlled by that wireless switch. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.